1. **State the problem:** We want to find the limit $$\lim_{n \to \infty} n\left(\sqrt{2n^2+1} - \sqrt{2n^2-1}\right).$$
2. **Use the conjugate to simplify:** To simplify the expression inside the parentheses, multiply and divide by the conjugate:
$$n \left(\sqrt{2n^2+1} - \sqrt{2n^2-1}\right) \cdot \frac{\sqrt{2n^2+1} + \sqrt{2n^2-1}}{\sqrt{2n^2+1} + \sqrt{2n^2-1}}.$$
3. **Apply difference of squares:** This gives
$$n \cdot \frac{(2n^2+1) - (2n^2-1)}{\sqrt{2n^2+1} + \sqrt{2n^2-1}} = n \cdot \frac{2}{\sqrt{2n^2+1} + \sqrt{2n^2-1}}.$$
4. **Simplify numerator and denominator:** The numerator is 2n. The denominator is
$$\sqrt{2n^2+1} + \sqrt{2n^2-1}.$$
5. **Factor out $n$ inside the square roots:**
$$\sqrt{2n^2+1} = \sqrt{n^2(2 + \frac{1}{n^2})} = n\sqrt{2 + \frac{1}{n^2}},$$
$$\sqrt{2n^2-1} = n\sqrt{2 - \frac{1}{n^2}}.$$
6. **Rewrite the denominator:**
$$n\left(\sqrt{2 + \frac{1}{n^2}} + \sqrt{2 - \frac{1}{n^2}}\right).$$
7. **Substitute back:** The expression becomes
$$\frac{2n}{n\left(\sqrt{2 + \frac{1}{n^2}} + \sqrt{2 - \frac{1}{n^2}}\right)} = \frac{2}{\sqrt{2 + \frac{1}{n^2}} + \sqrt{2 - \frac{1}{n^2}}}.$$
8. **Take the limit as $n \to \infty$:** Since $\frac{1}{n^2} \to 0$, we get
$$\lim_{n \to \infty} \frac{2}{\sqrt{2 + 0} + \sqrt{2 - 0}} = \frac{2}{\sqrt{2} + \sqrt{2}} = \frac{2}{2\sqrt{2}} = \frac{1}{\sqrt{2}}.$$
9. **Final answer:**
$$\boxed{\frac{1}{\sqrt{2}}}.$$
Limit Sqrt Difference 20A899
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